Exceedingly valuable as these are, especially in the matter of saving time, to the experienced quantity surveyor, the beginner should adopt them gradually and with caution. It is better to work slowly than to run the risk of a mistake. Probably, also, though the above abbreviations are customary, no two surveyors use them all, or if so, in the same sense necessarily; while the extremely practised man will originate others, which he will himself understand with ease, and use them freely. There is, in fact, no fixed rule in the matter beyond that the use of abbreviations is customary, and those in the above list, being in common use, are generally understood.